This invention relates generally to vehicle steering devices, and more particularly, to a system and a method for detecting a motor shorting relay failure.
The term “active steering” relates to a vehicular control system, which generates an output that is added to or subtracted from the front steering angle, wherein the output is typically responsive to the yaw and/or lateral acceleration of the vehicle. Active front control steering may improve vehicle-handling stability on a variety of road conditions. Stability control may be continuously active. For higher vehicle speeds, vehicle sensitivity of steering may be smaller. At lower vehicle speeds, park solution sensitivity may be increased and driver workload reduced. Thus, in some situations, an active steering control system may react more quickly and accurately than an average driver to correct transient handling instabilities. In addition, active steering can also provide for variable steering ratios in order to reduce driver fatigue while improving the feel and responsiveness of the vehicle. For example, at very low speeds, such as that which might be experienced in a parking situation, a relatively small rotation of the hand-wheel may be supplemented using an active steering system in order to provide an increased steering angle to the steerable road wheels.
An active rear steering (ARS) system utilizes a three phase brushless DC motor to position rear wheels of a vehicle. When the active rear steering system is not activated, it is desirable to short three phase windings of the DC motor together by closing a pair of electrical contacts to generate a braking force to prevent movement of the rear wheels by the DC motor. If the pair of electrical contacts does not have a closed operational position when the active rear steering system is not activated, the braking force is not generated.
Alternately, when the active rear steering system is activated, it is desirable to open the pair of electrical contacts to allow desired operation of the DC motor. It is further desired that the electrical conductivity of the two contacts of the motor shorting relay be verified. If the pair of electrical contacts does not have an open operational position when the active rear steering system is activated, the operation of the motor is degraded. In addition, partial failure of the relay cannot be detected.
There is a recognized need for a system and a method for detecting a motor shorting relay failure.